In the
automotive world, a lot of manpower and money is being put into research and
development of systems to help boost fuel economy. The most common system today
is a hybrid arrangement that uses batteries and electric motors to help propel
the vehicle. Another green system is a KERS flywheel like the one used on the Porsche 918 RSR racecar.

The KERS system on the Porsche is activated with a push button to give the car
added performance. Volvo is set to start testing its own version of KERS on the
public roads of Sweden after receive a grant from the Swedish Energy Agency.

"Our aim is to develop a complete system for kinetic energy recovery.
Tests in a Volvo car will get under way in the second half of 2011. This
technology has the potential for reducing fuel consumption by up to 20 percent.
What is more, it gives the driver an extra horsepower boost, giving a
four-cylinder engine acceleration like a six-cylinder unit," relates Derek
Crabb, Vice President VCC Powertrain Engineering.

The KERS flywheel that Volvo will use spins at
up to 60,000 RPM and gets its energy for the forces created when braking. That
rotational inertia is then transferred to the rear wheels via a special
transmission. In the Volvo system, the combustion engine will be switched off
as soon as braking starts and then the energy in the flywheel will be used to
propel the vehicle from a stop and help it accelerate.

This sort of system will be most effective in stop and go city driving. Volvo
estimates that the combustion engine might be able to be turned off as much as
half the time. When combined with the combustion engine the energy in the flywheel
could add as much as 80hp to the vehicle and increase performance while
allowing the car to be more fuel-efficient.

The Volvo flywheel will be made from carbon fiber instead of steel for maximum efficiency.
The flywheel measures a diameter of 20cm and weighs 13 pounds. It also spins in
a vacuum to minimize losses.

"We are not the first manufacturer to test flywheel technology. But nobody
else has applied it to the rear axle of a car fitted with a combustion engine
driving the front wheels. If the tests and technical development go as planned,
we expect cars with flywheel technology to reach the showrooms within a few
years," says Derek Crabb. He concludes: "The flywheel technology is
relatively cheap. It can be used in a much larger volume of our cars than
top-of-the-line technology such as the plug-in hybrid. This means that it has
potential to play a major role in our CO2-cutting DRIVe Towards Zero
strategy."

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